Gabriella439

I'm writing this post to publicly come out as trans (specifically: I wish to transition to become a woman).

This post won't be as polished or edited as my usual posts, because that's kind of the point: I'm tired of having to edit myself to make myself acceptable to others.

I'm a bit scared to let people know that I'm trans, especially because I'm not yet in a position where I can transition (for reasons I don't want to share, at least not in public) and it's really shameful. However, I'm getting really

chrisdone

Statically checked overloaded strings

This gist demonstrates a trick I came up with which is defining IsString for Q (TExp a), where a is lift-able. This allows you to write $$("...") and have the string parsed at compile-time.

On GHC 9, you are able to write $$"..." instead.

This offers a light-weight way to enforce compile-time constraints. It's basically OverloadedStrings with static checks. The inferred return type

andymatuschak

A composable pattern for pure state machines with effects

State machines are everywhere in interactive systems, but they're rarely defined clearly and explicitly. Given some big blob of code including implicit state machines, which transitions are possible and under what conditions? What effects take place on what transitions?

There are existing design patterns for state machines, but all the patterns I've seen complect side effects with the structure of the state machine itself. Instances of these patterns are difficult to test without mocking, and they end up with more dependencies. Worse, the classic patterns compose poorly: hierarchical state machines are typically not straightforward extensions. The functional programming world has solutions, but they don't transpose neatly enough to be broadly usable in mainstream languages.

Here I present a composable pattern for pure state machiness with effects,